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Nick H
Dodge Dakota
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1/21/2008
00:51:05
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 Subject: Lack of heat.... stumped
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I've replaced my thermostat twice in the past 2 weeks looking for easy methods to cure my lack of heat. Both times I blew threw the heater core hose (one coming off the water pump)and had little resistance doing so. Both times after I had great heat for about 20 minutes, then it goes back to cold. The temp gauge shows about 1/3 and is rock solid. I'm starting to think the heater core may be partly clogged after a few minutes of use? I had to replace the water pump this past summer due to the bearing go out and there may have been some metal shavings circulated into the system.
I've also heard someone say the mix door may not be working properly but how would I check that, and where is it? This is a 96 3.9L
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OBIO3
Dodge Dakota
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1/21/2008
01:04:42
| RE: Lack of heat.... stumped
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I think your either air locked or they gave you the wrong pump. The older ones bolt right on but they rotate in the reverse direction meaning it would be turning backwards. I think I got this correct. If not correct me >
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mike stager
Dodge Dakota
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1/21/2008
10:53:41
| RE: Lack of heat.... stumped
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Nick, if you had a blocked heater core, it would take a lot longer for you to get "heat" so I doubt you have a core issue.
I'd have to agree with a possible water pump problem. You may have a circulation problem. That's what I've got going on.
I've heard that some of the re manufactured waterpumps can have problems giving proper circulation.
First check what kind of heat you are getting with the hoses going into and out of the core. Also, and more importantly, check to see if you are getting pressure built up in the cooling system. When it gets up to temp, the upper radiator hose should be hard and hot. If you don't have enough pressure in the system, the pump is going to have a harder time pushing coolant through the heater hoses ( they are much smaller than anything else the cooling system has, so they are the path of most resistance ).
My truck gives me the best heat when I'm running @ 1500rpm, and poor heat @ idle.
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Nick H
Dodge Dakota
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1/21/2008
11:58:33
| RE: Lack of heat.... stumped
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Well the water pump is less then 5 months old, and maybe 1000 miles. The pump I removed and the pump I installed were exactly the same. The truck had good heat for a while after but it literally has no heat as of now. It seems to also be building pressure because when I removed the rad. cap it was rushing out the rad, as it had good force to it when I pulled the heater core hose off.
As for the checking the hoses. When the truck first got the thermostat replaced both times. After the thermostat opened the upper rad hose was hot and returning water back to the radiator from what I could tell. The hose did not feel hard really though, and I thought that was a good sign, showing that the thermostat has opened? Correct me if I'm wrong. Both heater core hoses were hot, but I have not checked them since the heat has stopped coming out.
What could cause a lack of flow or pressure? The reason I'm thinking it's a core clogging up is because if there was a bad water pump, would the temp not rise a lot more due to the poor flow of coolant though the block and head.
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Nick H
Dodge Dakota
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1/21/2008
13:51:14
| RE: Lack of heat.... stumped
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Are you sure about there being any kind of difference in the flow for the newer and older pumps. I've got pics of both the 87-89 and 93-96 pumps. It appears that they both flow the exact same direction.
http://www.car-stuff.com/store/images/prodimage/images/WORLDPAC/W01331624691GMB.JPG
http://www.car-stuff.com/store/images/prodimage/images/WORLDPAC/W01331615866GMB.JPG
I've also looked up the 90-92's and they also show the same direction for the coolant flow according to the impeller direction.
Not to mention when I purchased the pump, the only difference were.. pressed on or bolt on pulley, and threaded or non threaded heater hose. I matched up both of those with my previous pump. Can you varify there being a different flowing pump for the 3.9 v6?
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OBIO3
Dodge Dakota
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1/21/2008
15:29:19
| RE: Lack of heat.... stumped
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If you had heat for a while from the new pump, I'm now thinking you have a problem with the air dam not working, not switching from cold air to heater air
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Nick H
Dodge Dakota
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1/21/2008
16:27:52
| RE: Lack of heat.... stumped
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How can I check if the air dam is working properly and where exactly is it? I've never had a heater system of this sytle.
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OBIO3
Dodge Dakota
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1/21/2008
16:41:49
| RE: Lack of heat.... stumped
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I have never had a reason to take mine apart yet. Mine is a 99 4x4 CC 5.2L.. It's all going to be behind the dash obviously. 2 thoughts -- 1 is the dam switching from air to heat and the other is going from hot air to cooler air. Something came lose or broke. All a guess really. Your going to need a good book for sure.
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Nick H
Dodge Dakota
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1/21/2008
21:07:05
| RE: Lack of heat.... stumped
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Would the air damn just stop working properly while the heat was working fine, no setting touched, truck sitting there idle. Then work again 2 weeks later under the exact same conditions (thermostat swap and blew air through the heater core by mouth). Not sure if this is a function of the air damn but. If you slide the temp bar on the HVAC controls from Hot to cold, you can feel really cold air on the cold side coming out the vents and when you slide it back to the hot side, the air gets warmer but not enough to actually heat the cabin.
I'd love to just go out and work on the truck right now but it's like 0 degrees outside!
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Jimmy9190
Dodge Dakota
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1/21/2008
21:48:39
| RE: Lack of heat.... stumped
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There was a post on here a few years ago from a guy who had heat problems too and he posted how he back flushed the heater core with a water hose and cleared it all out and the heat worked great. Maybe that's what's wrong with yours. Hopefully you can still find it in a search here.
Jimmy
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OBIO3
Dodge Dakota
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1/21/2008
22:41:55
| RE: Lack of heat.... stumped
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Now that you stated blowing through the heater core by mouth, your problem goes back to the most likely. You need to back flush with water to get things moving like needed.
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OBIO3
Dodge Dakota
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1/21/2008
22:54:44
| RE: Lack of heat.... stumped
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Here's another thing.You or someone doing the water pump replace may have used the wrong anti freeze and mixed in old type with what comes in these trucks, it will gel and plug the heater first as it goes through the chemical reaction.
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Mikey
Dodge Dakota
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1/22/2008
17:48:47
| RE: Lack of heat.... stumped
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If your engine gauge is not reading hot then it's your fluid that's not getting hot enough. Cold fluid means cold heater core.
If your fluid was hot, but the heater wasn't blowing hot air then maybe your heater core is plugged.
If you don't have the same problem as me (I have a post on the V8 board), then I would have to agree with OBIO3 and say that you have air in the system.
After everything is good and warm try squeezing all of your hoses to the heater core and upper rad hose(which is the highest part of the system, so air likes to sit there)but keep everything topped up in the rad so that you can see any air bubbles that come out.
Also, take the tube off of the reservoir at the rad cap and see if you can blow into it and hear bubbles coming through into the reservoir. If you can't then you have to take it off and check for crud that has built up inside ie.. your engine is not topping itself up properly like it should. Or it's possible that you have a bad rad cap.
If your engine gauge is not building properly try taking the rpm's up to 2500 for awhile(5-10 mins) and see if your gauge moves up to 100.
Let me know what happens when you check these things.
Good luck!
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Nick H
Dodge Dakota
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1/22/2008
23:52:42
| RE: Lack of heat.... stumped
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Well I did a coolant flush tonight. Here are my findings so far. My system will not build pressure. I had decent heat, (drove around for 15 min or so, had temp up to normal range on gauge. Could still open the rad cap with no pressure being released what so ever. The coolant level had gone down just a tad so I topped it off. Squeezed both of the heater core hoses, got some bubbles, Repeated process, and continue to get some bubbles. Topped off coolant again, drove around for 5 min, still no pressure at rad cap. The heat is working but still not like it should at all times. I have not noticed any leaks or spots anywhere in the snow where the truck gets parked, no coolant smell or wet carpet inside. No signs of coolant in the oil, or exhaust in the coolant. Coolant level stays the same when the car sits for days at a time. Could this just be a really tough air bubble? If so how else can I go about getting it out?
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mike stager
Dodge Dakota
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1/23/2008
00:50:20
| RE: Lack of heat.... stumped
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Bring it to a shop and have it pressure tested. They'll pump the system up to 16psi and let it sit and see how long it takes for the pressure to bleed down (It should hold for quite a while if the system is good )
If you are losing pressure, it could be from the cap, or in rare circumstances it could be a crack that is allowing pressure to escape without coolant losses that are obvious. Had that happen with a thermostat housing with a hairline crack.
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Nick H
Dodge Dakota
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1/23/2008
11:24:50
| RE: Lack of heat.... stumped
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I'm going to guy buy a coolant pressure tester tonight. After I pump the system up to 16 psi, should I start checking for leaks while pressurized?
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Mikey
Dodge Dakota
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1/23/2008
18:40:43
| RE: Lack of heat.... stumped
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Was it a rebuilt water pump?
Cause it's possible that the impeller was placed on backwards when it was rebuilt by whatever company did the rebuild.
That means that the pump is turning in the proper direction, but the impeller isn't pushing the rad fluid through with enough force.
I'm having the same problem as you after I changed the water pump and it's the only thing that I can think of.
Let me know.
Also check on that coolant reservoir by trying to blow through it.
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mike stager
Dodge Dakota
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1/23/2008
18:58:07
| RE: Lack of heat.... stumped
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Yes, it would be a perfect time to look for leaks with pressure on the system, particularly because you won't have to worry about that nasty fan belt taking a piece of loose clothing for a nasty ride ;)
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Matt Busby
Dodge Dakota
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1/23/2008
22:30:25
| RE: Lack of heat.... stumped
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Might have already been mentioned, but for sure a clogged heater core. Take the hoses off and flush and backflush multiple times. Might take a couple tries as it will clog up agaiin as you drive it until it is mostly caught.
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Nick H
Dodge Dakota
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1/30/2008
01:07:15
| RE: Lack of heat.... stumped
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Update:
Well I have not had a chance to pressure test the system, as I've been using the truck to haul stuff while moving the past week or so. Everything was working ok... decent heat, then all the sudden the heat was rather poor again and for the first time the temp gauge got a bit over half way. I stopped and checked the upper rad hose it was as stiff as could be and tons of pressure in the system. Coolant tank was showing very little fluid.
Started engine again and held the rpms at 3k for a bit. The temp gauge shot back down to less then 1/3. Drove the rest of the way home, virtually no heat. Got home and the upper hose was soft again and the coolant tank was up to the full mark again. Still almost no heat.
Also yes the water pump was a rebuild. What is the propper impeller direction, is there any way to test out my pump while still on the engine.
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mike stager
Dodge Dakota
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1/30/2008
08:26:45
| RE: Lack of heat.... stumped
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I'd have to say you may want to bring it into a shop and pay the diagnostic fee and have them figure out what is going on.
AT the very least, get that pressure tester and see what happens with your heat when you have no pressure, and when you pump up the pressure to 16psi. I'm betting there'll be a difference.
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